At least five people were shot Thursday at a Southern California high school, where police are searching for the suspected shooter, according to local officials.

“We have multiple victims down,” Sergeant Bob Boese of the Los Angeles County Sheriff’s Department said in a statement. “Our deputies are doing a systematic search of the campus, trying to locate the suspect.”

The Santa Clarita Valley Sheriff’s Station said in a tweet: “This is an active shooter situation. The suspect described to be a male Asian, black clothing is outstanding.” In another tweet, the department warned residents to “LOCK DOORS and stay inside.” Authorities believe the shooter, who was a student at the school, acted alone.

The shooting took place at Saugus High School in Santa Clarita, about 40 miles north of Los Angeles. More than 2,300 students attend the school, and some of them were seen in aerial footage being escorted from the school by police. NBC Los Angeles notes that two ambulances have also been seen leaving the school.

At just before 8:30 a.m. local time, the Henry Mayo Hospital in Santa Clarita tweeted that it had received two victims from the shooting and three more were “en route.”

The Los Angeles Times has further details about the scene at the high school following the shooting:

Several students were placed on gurneys and transported to ambulances in the school’s parking lot. Many of the wounded people were being treated in a grassy area on the campus. At least person was found wounded in the school’s choir room.

The paper also reports that police are looking for the shooter in “the area of brush behind the high school adjacent to a creek where authorities suspected the teen might be hiding.”

Authorities have placed nearby schools on lockdown as the search for the shooter continues.